2022 Fiscal Year Annual Research Report
Largescale numerical investigation on the potential of MTL to produce supershear earthquakes
| Project/Area Number |
22H01573
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| Allocation Type | Single-year Grants |
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| Research Institution | The University of Tokyo |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
加藤 愛太郎 東京大学, 地震研究所, 教授 (20359201)
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| Project Period (FY) |
2022-04-01 – 2026-03-31
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| Keywords | off-fault damage zone / visco-plasticity / rupture speed / super-shear / sub-Rayleigh |
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| Outline of Annual Research Achievements |
As planned, we implemented visco plastic model to simulate off-fault damage zone and thereby control the rupture speeds. We derived analytical solutions to reduce the high computational cost associated with plastic models. We verified the implemented models by comparing with the standard engineering benchmarks. The developed numerical schemes were implemented in HPC enhanced environment to simulate large scale models. We simulated both super shear and sub-Rayleigh events on the Palu Koro fault and demonstrated that the visco plastic model reduces the rupture speed closer to the rupture speed observed at the 2018 super shear event of the Palu Koro fault. This is an important step in the model development since it enables to reproduce rupture speeds closer to the observed in nature.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The main objective of FY 2022 was to simulate off-fault damage zone and improve computational efficiency. We successfully implemented necessary plastic models in HPC-enhanced code and verified. By simulating a model of Palu-Koro fault consisting of 5.6 billion elements and 1 billion nodes, we successfully demonstrated that the developed model can reduce the rupture speeds closer to the field observations and the developed numerical code is capable of simulating large scale models. Further, we made a significant progress in reducing computation cost involved in numerical integration, which will contribute to reduce computational time in our future simulations. The completion of all these major items planned for FY2022 made us conclude that the research progressed well.
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| Strategy for Future Research Activity |
We plan to verify the developed rupture simulator comparing with available benchmark models, and simulate the 2018 super-shear event of Palu-Koro fault as a qualitative validation. Further, we plan to collect data from J-SHIS and other institutions to build an accurate geometric model of 200km long stretch of the Median Tectonic Line. Mesh around the fault will be refined such that fault geometry will be accurately represented and rupture process accurately simulated. The rest of the domain will be refined such that seismic wave propagation is accurately captured up to 8Hz; the refined model is expected to consist of 5~8 billion elements. We will continue improving the code to best utilize the Univ. of Tokyo's supercomputer for conducting large-scale simulations.
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